基于探地雷达的土壤水分测定方法研究进展

农田和小流域尺度土壤水分空间和时间分布信息的快速、准确、无损获取是土壤学、农学以及生态环境学等相关科学研究的重要需求.探地雷达作为一种新型地球物理技术, 近年来在多个领域有了应用和推广.本文针对探地雷达技术在土壤水分监测方面应用的科学问题, 在总结国内外相关研究的基础上, 重点阐述了探地雷达技术测定土壤含水量的基本原理、土壤含水量和土壤介电常数的常用关系式、探地雷达技术测定土壤含水量的研究方法及其在国内外的研究进展, 评价了各方法的优势和不足及其在农田土壤中的适用性, 并提出存在的问题和研究展望, 以期为相关科学研究以及探地雷达在我国农田土壤上应用开创新的领域提供参考.     

利用微波反射效应测定土壤强度的研究

传统的土壤强度测定方法均需直接接触土壤,该文提出一种利用微波反射效应测定土壤强度的遥测方法。采用一套简单的试验装置以测定土壤的微波反射损失并用之研究土壤的含水量、容重、土壤类型和贯入阻力对微波反射损失的影响。试验结果表明,在单对数坐标中土壤的微波反射损失随其圆锥指数增加而呈线性减少。     

土壤微生物量碳周转分析方法及其影响因素

简述了目前国内外常用的3种测定土壤微生物生物量C周转分析方法及其影响因素、改进的土壤微生物生物量C周转动力学测定方法及其应用前景,并分析了国内外不同生态环境、土壤质地和耕作管理制度等的土壤微生物生物量C周转的研究结果。     

气量法快速测定土壤含水量技术

气量法作为一种新的土壤水分测定方法,具有便捷、快速、准确的特性。准确及时测定土壤水分含量有利于研究和了解水土流失变化规律、土壤水分动态变化规律和空间立体分布;同时掌握不同植物在同一时期对土壤水含量的不同要求,同一植物在不同时期对土壤水分含量的不同要求以及土壤水分含量对其产量的影响。其测定方法可分为体积法、失重法。气量法是一种稳定、准确、快速的土壤含水量测定方法,气量失重法与气量体积法相比较,气量失重法所需仪器更为简单,操作更为简捷。可适用于农业、林业试验土壤含水量的测定,另外此装置还可以应用到其他农业科学研究。     

TDR研制与应用方面的若干进展

通过分析近年来国内外关于TDR的文献,总结了TDR研制与应用方面的若干新进展,概括了在使用TDR时应注意的几个问题。结果表明,线圈型TDR探针可很好地解决TDR探针在物理长度上的限制;多功能TDR探针可用来同时测定含水量与基质势、含水量与土壤热学性质、含水量与盐度和温度。江温度在5－45℃之间变化时随着温度的升高,TDR在沙漠土中测定的土壤含水量降低,而在粘壤土和有机质含量高的土壤测定的土壤含水量值升高。TDR探针应以合适的角度插入土壤,同时尽量避免摇摆、两探针不平行插入等误操作。     

TDR研制与应用方面的若干进展

通过分析近年来国内外关于TDR的文献，总结了TDR研制与应用方面的若干新进展，概括了在使用TDR时应注意的几个问题。结果表明，线圈型TDR探针可很好地解决TDR探针在物理长度上的限制；多功能TDR探针可用来同时测定含水量与基质势、含水量与土壤热学性质、含水量与盐度和温度。当温度在5～45℃之间变化时随着温度的升高，TDR在沙壤土中测定的土壤含水量降低，而在粘壤土和有机质含量高的土壤测定的土壤含水量值升高。TDR探针应以合适的角度插入土壤，同时尽量避免摇摆、两探针不平行插入等误操作。     

农田生态系统土壤呼吸测定方法研究进展

土壤呼吸是全球碳循环和气候变化的重要影响因子之一,农田生态系统是全球碳循环中最活跃的部分,研究农田生态系统土壤呼吸对农田固碳减排具有重要的意义。文章综述了目前国内外农田土壤呼吸的测定方法和组分分离方法,讨论了各方法的原理、技术、优缺点和适用范围,认为动态气室法是土壤呼吸测定的首选方法,必要时可与微气象法配合使用。根分离法简便准确,是国内普遍采用的农田土壤呼吸组分分离方法。文章还指出,农田生态系统土壤呼吸测定时应做到规范测定方法、确保跟踪时间、扩大研究范围,以确保测量精度和代表性。     

Karl Fischer滴定法测定土壤含水量

土壤水分的测定方法有很多种,烘干法是目前国际上测定土壤水分的标准法。这种方法比较准确,且便于大批样品测定,故为最常用的方法。但是它也存在一些比较明显的缺点,如在测定含有挥发性物质的土壤含水量时,因为烘干法测定的是挥发性物质总量,而不单纯是土壤水分含量,因而得到的结果较实际含水量偏高。Ｍ．Ｋ．Ｚｅｌｌｉｓ、Ｊ．Ｓ．Ｂｅｌｌ、ＬｙｌｅＰｒｕｎｔｙ等人将ＫａｒｌＦｉｓｃｈｅｒ滴定法用于测定土壤水分含量取得了较好的效果。这种方法特别适用于测定含有挥发性物质或情况不明的土壤含水量。ＫａｒｌＦｉｓｃｈｅｒ滴…     

土壤可溶性有机氮测定方法研究进展

可溶性有机氮(DON)是土壤中生物可利用有机氮库的主要成分,是最为活跃的有机氮形态之一。DON在土壤中的迁移和转化是土壤氮素地球生物化学循环的重要一环,与氮素养分供应、损失等过程密切相关。然而缺失准确、可靠的土壤DON分析方法严重限制了DON的相关研究进程。本文综述了近年来国内外土壤浸提液和水体中DON测定方法,重点比较了不同可溶性总氮(DTN)测定方法以及不同前处理方法对提高DON测定结果准确性的影响。     

土壤中砾石含量的测定方法研究进展

石质土壤中含有大量砾石,大量砾石的存在会影响土壤理化特性和水力特性。土壤中砾石含量的研究会影响土石介质的生产力评估、水文及风化过程的研究水平。本文主要介绍了国内外土壤中砾石含量的现有测定方法,对环刀取样法、挖坑法、Viro插钎法,γ射线法、探地雷达及电阻率断层扫描技术的实际应用进行了讨论。在实际研究中应根据实际情况选择合适的砾石含量测定方法。土壤中砾石含量的测定应该引起国内相关研究的重视,为土壤研究提供重要信息并为土壤学研究水平的提高提供帮助。     

Die Validierung von Bodenwasserhaushaltsmodellen mit Hilfe von TRIME-TDR,Tensiometermessungen sowie thermogravimetrischen Bodenfeuchtebestimmungen

The validation of soil water balance models based on measurements of soil water contents by gravimetry and by TRIME-TDR and of soil water suctions determined by tensiometer In this study different measuring techniques for determining soil water contents and soil water suctions were analysed for their suitability for the validation of soil water balance models. For this purpose a period of three years with continuous data of soil water contents measured by TRIME-TDR and soil water suction measured by tensiometer were available. Additionally soil samples at different times were taken for gravimetric moisture analyses. These measurements were compared with the corresponding simulation results of a soil water balance model. This soil water balance model consists of the determination of evapotranspiration according to Penman-Monteith and the calculation of soil water fluxes based on the Darcy-equation. The results indicate the higher suitability of TDR-measurements for evaluating the goodness of fit between the simulated and the calculated results in comparison with the other measuring techniques used in this study, especially in the context of general soil water dynamics. The tensiometer data show the limited measuring range as a well known disadvantage of this technique.     

Performance of a non‐nuclear resonant frequency capacitance probe. II. Measurement of dryland crop water use

Abstract

Resonant frequency capacitance techniques have been recently developed as a safe and reliable method for measuring water content of various materials. A previous study with a commercial capacitance probe (Troxler Sentry 200‐AP) showed it to be a safe, reliable, and a rapid method of in situ measurement of soil water content in the field provided it is calibrated for individual soils. Further testing of this resonant frequency capacitance probe was done to evaluate the performance of the probe by comparing results of field measured crop water use to those reported in similar studies using other methods of determining in situ soil water content in the field. These tests were done in two field experiments which were conducted during the summer of 1994 using corn and sorghum as the indicator crops. The experimental field was the same used to calibrate the capacitance probe in the previous study. Treatments consisted of three plant populations of corn and four plant populations in two cultivars of grain sorghum. The crop water use for corn and sorghum averaged over all treatments were 452 and 424 mm, respectively. The measured crop water use values for corn and sorghum were comparable to the crop water use values reported in several similar previous studies using different in situ soil water measuring instruments.     

东北黑土区TDR测定农田土壤含水量的室内标定

土壤水分标定是利用TDR监测农田土壤水分过程中的必要环节.以东北黑土区农田土壤剖面深度上的4种典型介质（黑土层、母质层、过渡层、砂砾层）为试验对象,利用“由湿到干”的土柱试验方法,用烘干法对TDR进行室内标定研究.结果表明：1）TDR内置土壤标定曲线测定的含水量明显低于烘干法测量的含水量.在TDR法土壤含水量标定时,指数关系比线性关系具有更高的标定精度.2）单一介质的TDR法土壤含水量标定曲线对自身介质的标定精度高（最大绝对误差3.2％）.3）混合介质的TDR法土壤含水量标定曲线的标定精度较高（最大绝对误差6.6％）,可用于不同介质TDR法土壤含水量标定.本研究结果可用于研究区及类似区域修订TDR法含水量测定结果.     

Development of a quick on‐farm test to determine nitrate levels in soil

Crop management can be optimized and nitrogen (N) losses can be reduced with a better knowledge of soil‐nitrogen availability, especially if this information becomes directly available on‐site in a fast and cost‐effective way. In this paper, simple on‐farm methods to determine nitrate‐N in field‐moist soil samples immediately after sampling are described. The procedures include volumetric soil sampling, extraction based on manual shaking with tap water as universally available extractant, filtering soil/extractant mixtures on‐site, on‐site determination of the soil water content, and reflectometric nitrate measurements based on test strips. Using correction factors can compensate the impact of the temperature during the final nitrate measurement. An excellent agreement was found between the developed quick‐test procedures and the standard laboratory procedure. The proposed quick‐test has great potential to enable economical savings for farmers as well as benefiting the environment.     

赣南地区水土流失评价模型及其影响因子获取方法研究

以模型和"3S"技术为基础,介绍了赣南地区水土流失及其影响因子的评价方法和获取途径。在弄清各因子含义和算法的基础上,确定和构建了适合赣南地区侵蚀环境的水土流失评价模型及其因子值获取方法;同时对赣南地区林下水土流失区的水土保持生物措施因子B值以及水土保持工程措施因子E值的算法进行了有益的尝试。     

土壤裂隙及其优先流研究进展

土壤在干燥脱水的过程中易收缩产生裂隙。裂隙的产生是土壤性质与外界条件等多种因素综合作用的结果,其形态结构也非常复杂,难以准确描述。裂隙能够作为优先流的路径,增加农田水分和养分的流失以及地下水污染的风险。本文总结和归纳了裂隙产生的影响因素、裂隙的表征指标与测定方法、裂隙导致的优先流的研究方法、裂隙对优先流的影响和模拟等方面的研究进展。今后应进一步加强裂隙产生机理的全面深入的研究;构建和完善裂隙三维指标体系及其测定方法;推进裂隙导致的优先流的定量化和数学模拟研究;加大田间原位裂隙及其优先流的研究。     

土壤有机质测定方法述评与展望

有机质是土壤的重要组成部分,是判定土壤质量动态变化的重要标准。为了便于了解当前土壤有机质测定方法的优点和局限性,利于今后有机质研究和测定工具的开发,本文对当前测定有机质的方法,包括干烧法、湿烧法、化学氧化法、灼烧法和土壤有机质光谱测定法进行了阐述,分析了各方法的优缺点以及研究中适宜选择的方法,并对当今农业的需求和测定方法的不足,提出了研究无损、原位测量有机质工具的构想,展望了土壤有机质快速测定方法的发展趋势,以此为精准农业的实施和农业的可持续发展,提供基本的信息及建议。     

MEASUREMENT OF PORE SIZES IN FINE-TEXTURED SOILS: A REVIEW OF EXISTING TECHNIQUES

Pore size distributions obtained from the relationship between moisture content and suction are not dependable in fine-textured soils because of shrinkage. To overcome this problem, methods such as nitrogen sorption, mercury intrusion porosimetry, non-polar liquid desorption and thin sectioning have been used. In order to pre-dry samples without changes in the pore system, freeze-drying, organic liquid replacement of soil water, and critical point drying techniques have been employed. These methods of soil drying and pore size measurement are described and compared, and the validity of their use in soil studies is examined. The measurement of pore sizes by water desorption is also discussed.     

Using selected soil physical properties of seedbeds to predict crop establishment

Seedbed preparation can involve a wide range of tillage methods from intensive to reduced cultivation systems. The state or quality of the soil to which these tillage methods are applied for cereal crop management is not easily determined and excessive cultivations are often used. Seedbed preparation is crucial for crop establishment, growth and ultimately yield. A key aspect of the soil condition is the soil physical environment under which germination, growth and establishment occur. Crucially this affects factors such as temperature, water content, oxygen availability, soil strength and ultimately the performance of a seedbed. The dynamics of soil physical properties of a range of seedbeds and how they relate to crop establishment are considered in this paper. Significant interactions between cultivation techniques, physical properties of the seedbed in terms of penetration resistance, shear strength, volumetric water content and bulk density and the interaction with crop establishment were identified. A soil quality of establishment (SQE) model was developed for the prediction of crop establishment based upon soil bulk density and cultivation practices. The SQE significantly accounted for ca. 50% of the variation occurring and successfully predicted crop establishment to a standard error of around 20 plants per m⁻² across contrasting soil types and environmental conditions.     

Container and Installation Time Effects on Soil Moisture,Temperature, and Inorganic Nitrogen Retention for an in situ Nitrogen Mineralization Method

Mineralization contributes significantly to agronomic nitrogen (N) budgets and is difficult to accurately predict. Models for predicting N‐mineralization contributions are needed, and development of these models will require field‐based data. In situ mineralization methods are intended to quantify N mineralization under ambient environmental conditions. This study was conducted to compare soil moisture and temperature in intact soil cores contained in cylinders to those in adjacent bulk soil, compare the effect of two resin‐bag techniques on water content of soil within cylinders, and assess the effect of installation duration on inorganic N retention by resins. The study was conducted at a dryland conventionally tilled corn (Zea mays L.) site and an irrigated no‐tillage corn site in eastern Nebraska. Soil in cylinders was slightly wetter (<0.05 g g^?1) and warmer (<1 °C) than adjacent soil. Soil water content was <80% water‐filled pore space (WFPS) at all sampling times and differed little between the two resin‐bag techniques. Greater soil water content and temperature conditions (though small) observed during most of the study period likely enhanced N mineralization within the cylinder compared to N mineralization in adjacent bulk soil, but the magnitude is likely much less than core‐to‐core variation normally observed in a field. Installing cylinders for more than 60 days resulted in loss of inorganic N from resins. Care is needed during installation to ensure that compaction of soil below the cylinder does not impede water movement through the intact soil core. The in situ method utilizing intact soil cores and resin bags replaced at 28‐ to 40‐day intervals is a viable method for measuring N mineralization.